Steel EN8
BS EN8 · AISI/SAE 1040
EN8 is a medium-carbon engineering steel from the British Standard series, equivalent to AISI 1040 and C40, stocked hot-rolled, cold-rolled, cold-drawn, annealed, normalized or quenched and tempered.
Values for the HR condition
EN8 tempers and conditions
EN8 is supplied in 6 conditions, soft to hard. HR is the default FabDigit quotes; the values on this page are for it.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
full/sub-critical anneal, softest condition | Pick when maximum softness/ductility is needed for cold forming, deep machining or stress relief before hardening. | 300 | 540 | 24 | 155 HB | — |
HRDefault Hot rolled | Most stocked form: hot-rolled black bar/plate for general machined parts that will be heat treated or used as-is. | 310 | 580 | 18 | 179 HB | — |
austenitize ~850 °C, air cool | Use for uniform fine-grained structure and predictable machining/strength in larger sections, typically before final machining or induction hardening. | 370 | 620 | 20 | 185 HB | — |
Cold rolled | Choose for thin strip/sheet with good surface and closer thickness tolerance; strength raised, ductility reduced. | 470 | 640 | 12 | 12 HRC | 10 % IACS |
Cold drawn | Bright, size-accurate bar for shafts and turned parts where no further heat treatment is planned; highest as-supplied yield of the unhardened conditions. | 540 | 660 | 12 | 201 HB | — |
Quenched and tempered | Choose for loaded shafts, gears, keys and studs needing higher yield and fatigue strength; hardenable depth limited to roughly 30–60 mm diameter. | 620 | 850 | 15 | 25 HRC | — |
What is EN8?
EN8 is a medium-carbon engineering steel from the British Standard series, equivalent to AISI 1040 and C40, stocked hot-rolled, cold-rolled, cold-drawn, annealed, normalized or quenched and tempered. It is the general-purpose bar for shafts, pins and fasteners at moderate strength and takes induction hardening on bearing surfaces; the default condition lists 310 MPa yield, 580 MPa tensile, 18 % elongation and 179 HB. Weldability is limited by the ~0.4 % C content (score 45), cold formability is modest (score 45), and there is no corrosion resistance. EN19 (4140) is the step up where higher through-hardened strength is needed. EN8 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). EN8 has a yield strength of 310 MPa (45 ksi) and a tensile strength of 580 MPa (84.1 ksi) — weaker than 83% of steel grades. Elongation at break is 18% and the elastic modulus is 205 GPa (29.7 Msi).
What is EN8 used for?
- Crankshafts
- Shafts
- Industrial bolts
Advantages
- Conducts heat well — 50 W/m·K (28.9 BTU/hr·ft·°F), better than 87% of steel grades
- High electrical conductivity — 10 % IACS, better than 83% of steel grades
Limitations
- Low strength — 310 MPa (45 ksi), worse than 83% of steel grades
- Low fracture toughness — 55 MPa·√m (50.1 ksi·√in), worse than 82% of steel grades
EN8 properties
Typical room-temperature values for EN8-HR; bars are the position among steel grades.
Physical3
EN8 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
EN8 has a yield strength of 310 MPa (45 ksi) and a tensile strength of 580 MPa (84.1 ksi) — weaker than 83% of steel grades. Elongation at break is 18% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
EN8 is rated for continuous service to 400°C (752 °F). It conducts heat at 50 W/m·K (28.9 BTU/hr·ft·°F), better than 87% of steel grades. Thermal expansion is 11.7 µm/m·K (6.5 µin/in·°F).
Electrical3
EN8 conducts electricity at 10 % IACS, better than 83% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (10/100), worse than 86% of steel grades.
Sustainability4
Producing a kilogram of EN8 takes about 25 MJ of energy and emits 2 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 30%.
Manufacturability8
EN8's machinability is good (60/100, better than 83% of steel grades); weldability fair (45/100); formability fair (45/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. EN8 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with EN8
Is EN8 easy to machine?
Machines readily in HR/normalized condition with carbide or HSS (≈60 % of AISI 1212); rough-machine before hardening and expect ~50 % rating and shorter tool life above 250 HB.
Can EN8 be welded?
Weldable with low-hydrogen electrodes but 0.4 % C demands 150–260 °C preheat, controlled interpass and post-weld stress relief/temper to avoid hard martensitic HAZ cracking.
Can EN8 be formed, bent or molded?
Hot forge 1050–1200 °C then normalize; cold bending is limited — use annealed stock and generous bend radii (>3 t).
Manufacturability
The process limits FabDigit's quote engine applies to EN8. Design inside these and the part quotes instantly; outside them it routes to an engineer.
CNC machining
| Machinability | Better60 / 100 |
|---|---|
| ISO material group | P.2 |
| Cutting speed (rough / finish) | 180 / 210 m/min |
| Minimum wall | 0.8 mm |
| Minimum internal radius | 1 mm |
| Drill depth limit | 5× diameter |
| Best surface (machined / polished) | Ra 1.6 / — |
| Hardenable after machining | No |
Sheet metal
| Formability | Better45 / 100 |
|---|---|
| Weldability | Better45 / 100 |
EN8 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| CBS 970 080M40 / EN8 | 0.36 – 0.44 | 0.4 |
| Si | 0.1 – 0.4 | 0.25 |
| Mn | 0.6 – 1 | 0.8 |
| Smax; EN8M free-cutting version 0.20–0.30 S | ≤ 0.05 | 0.03 |
| P | ≤ 0.05 | 0.03 |
| Fe | balance |
What surface finishes work on EN8?
No anodizing; protect by zinc/nickel/hard-chrome plating, phosphating, black oxide, paint or oiling — bare bar rusts quickly in humid storage.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Plating
CVD Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel EN8 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
How much does EN8 cost?
EN8 is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
EN8 — frequently asked
What is EN8 used for?
EN8 is typically used for crankshafts, shafts and industrial bolts. In short: workhorse English carbon bar.
What is the yield strength of EN8?
EN8 has a typical yield strength of 310 MPa (45 ksi) and a tensile strength of 580 MPa (84.1 ksi) — weaker than 83% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is EN8 easy to machine?
Reasonably — machinability is rated good (60/100, better than 83% of steel grades). Machines readily in HR/normalized condition with carbide or HSS (≈60 % of AISI 1212); rough-machine before hardening and expect ~50 % rating and shorter tool life above 250 HB.
Can EN8 be welded?
With care — weldability is rated fair (45/100). Weldable with low-hydrogen electrodes but 0.4 % C demands 150–260 °C preheat, controlled interpass and post-weld stress relief/temper to avoid hard martensitic HAZ cracking.
What surface finishes work on EN8?
No anodizing; protect by zinc/nickel/hard-chrome plating, phosphating, black oxide, paint or oiling — bare bar rusts quickly in humid storage.
Can EN8 be formed, bent or molded?
Hot forge 1050–1200 °C then normalize; cold bending is limited — use annealed stock and generous bend radii (>3 t).
What is the maximum service temperature of EN8?
EN8 is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between EN8-HR and EN8-CD?
HR is the default condition — most stocked form: hot-rolled black bar/plate for general machined parts that will be heat treated or used as-is. CD: bright, size-accurate bar for shafts and turned parts where no further heat treatment is planned; highest as-supplied yield of the unhardened conditions. Yield strength is 310 MPa in HR versus 540 MPa in CD.
How much does EN8 cost?
EN8 is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Can FabDigit make parts in EN8?
Yes — EN8 is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- BS 970 Part 1 / Part 3 — 080M40 (EN8) wrought steels — BSI (1991)
- GB/T 699 — Quality carbon structural steels (45 ) — SAC (2015)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating (carbon steel hardenability/tempering) — ASM International (1991)
- SAE J403 / ASTM A576 — AISI 1040/1045 carbon steel bars — SAE / ASTM (2017)
- Mysteel / 1688 — Mysteel (2025)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.